Main vent recommendation?

danmayer175 · January 20

My main is 65 ft long and about 1.5 cf volume. I have a single Gorton #2 on it now. Is adding another #2 worthwhile?

Long Beach Ed · January 20

Try running it with the vent removed. If the main heats much faster than with the single #2, then another addition may be indicated.

dabrakeman · January 20

Make sure this test is run with the system well warmed up both times. Typically one Gorton #2 would be considered enough for that volume though.

Big Ed_4 · January 20

What is the problem as to ask ?

danmayer175 · January 21

I ran two tests with the header already hot. Open 1/2" bushing saw steam in 2 minutes. With the #2 it was more like 3:30.

danmayer175 · January 21

https://forum.heatinghelp.com/discussion/comment/1836594#Comment_1836594

Last runout is slow to heat up.

delcrossv · January 21

What's on that runout? What vent on the rad? Riser to second floor?

Steamhead · January 21

https://forum.heatinghelp.com/discussion/comment/1836643#Comment_1836643

https://forum.heatinghelp.com/discussion/comment/1836644#Comment_1836644

Add the second #2. This will get steam to that last riser much more quickly.

danmayer175 · January 21

https://forum.heatinghelp.com/discussion/comment/1836664#Comment_1836664

There are 2 radiators, both have varivalves on middle setting. The second floor rad is slowest (and farthest from boiler). Every other runout is in the first half of the main, this one is the end of the line, just before the main vent.

dabrakeman · January 21

Obviously you can try slowing down some of the quicker radiators to help the balance. Adding the second #2 may help a bit as well. I would raise the main vents up on a nipple and antler. Looks like you have plenty of room.

delcrossv · January 21

What @dabrakeman said. You can also try a riser vent at the top of that runout and insulate as much of it as you can.

danmayer175 · January 21

I'm adding an antler tonight. I have the Gorton #1 that was on the main when I moved in, so I'll add that first and see if it helps. And then tune the Varivalves I have all over the house. I'm planning to replace them all, but it's a pricy proposition and this #1 is free to me!

danmayer175 · January 22

I added the antler and the #1 last night. I think it's about 30 seconds faster. The last radiator vents a little quieter and seems to be heating up faster.

Steamhead · January 22

Those street elbows don't have full-size 1/2" passageways. This can slow the venting rate. I'd change them to regular elbows and short nipples.

SteamingatMohawk · January 22

Be aware that the varivalves do not shut completely. At the minimum setting they are equavalent to a #4. See the chart.

https://www.heatinghelp.com/assets/documents/Vent-Valve-Comparison.pdf

dabrakeman · January 22

If you replace the street 90 I would also give it a longer nipple to raise the whole thing a bit more…

danmayer175 · January 23

https://forum.heatinghelp.com/discussion/comment/1837041#Comment_1837041

Dang it. I thought I was being smart getting fewer fittings.

ethicalpaul · January 23

i woudn't sweat it

danmayer175 · January 24

If I put a gauge on the end of this antler, and compare to gauge in boiler will I get an accurate measure of pressure drop in the main? After the vents have closed of course. There isn't some strange pressure zone in there, right? I can't see why there would, but I've been humbled by steam before.

delcrossv · January 24

Once the vents close, the pressure will be the same as the boiler pressure (assuming the rad vents are closed too). You may get a peek at the pressure drop in the interval between when the main vents close and the rad vents close. You can look it up. Jake Myron's book has that info.

ethicalpaul · January 24

You aren't likely to ever see any pressure difference between the boiler and the end of the main, not in a house anyway.

Main vent recommendation?

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